Some hybrid vehicles use a primary power source for the majority of the vehicle's propulsion needs and supplement that with an auxiliary power source, as needed. Certain driving conditions, such as the steep inclines and declines sometimes found on mountain roads, can present unique challenges for hybrid vehicles.
For example, when a hybrid vehicle is attempting to climb a mountain road with a significant grade, the electric motor may exhaust or at least diminish much of the stored charge on the battery. If the state-of-charge (SOC) of the battery falls beneath a certain threshold, the hybrid vehicle may have to rely on an internal combustion engine to provide supplemental propulsion power. In order to accomplish this task without resulting in a significant reduction in power that is noticeable to the driver, the operational interaction between the electric motor and the internal combustion engine may need to be specifically tailored to environments such as these.